Across populations, bottlenose dolphins (Tursiops sp.) exhibit a fission-fusion pattern of associations, in which group size and composition change fluidly throughout the day. Beneath this seemingly ephemeral social structure, considerable variation exists across study sites. While females typically have moderate bonds with one another within a large social network, male-male bonds are variable, though males typically take one of two strategies; some males encounter females individually for opportunities to breed while others cooperate within a first-order alliance to collectively herd females. In addition, multi-tiered alliances in which two first-order alliances cooperate to defend or assist in the theft of a female have been documented within Shark Bay, Australia. However, these patterns do not apply to all study sites, as intersexual bonds are strong within several bottlenose dolphin populations. Given the variation in the presence and complexity of male alliances, greater documentation of social structure and male mating strategies across study sites is needed to draw conclusions as to the ultimate factors behind alliance formation. As such, chapter one documents the inclusion of a new study site in the St. Johns River (SJR) in Northeast Florida where males form first and second-order alliances. In addition, variables from the SJR are included within a meta-analysis in chapter two, the first systematic examination of what variables correlate with alliance presence and complexity, with the conclusion that male-male competition best describes the patterns seen in male alliance formation. Chapter three builds upon this conclusion by examining seasonal trends in tooth rake marks, a proxy for aggression, across the sexes and males of two different mating strategies, ultimately highlighting the potential for non-reproductive aggression. Together, this work provides greater insight as to the social structure and mating patterns of bottlenose dolphins, as well as to the ecological pressures that result in complex sociality.